In recent years, performance and transaction capacity of electronic devices are rapidly advancing, and an amount of heat emitted by electronic components such as semiconductor elements are increasing. To keep an operational performance and a reliability of the semiconductor elements and others, a thermal conductive sheet capable of conducting heat to a heat sink or the like is being employed. A pyrolytic graphite sheet is superior in conducting heat along a surface thereof and is used as the thermal conductive sheet. (see PLT 1, for example)